Mixture control system for an internal combustion engine with controlled injection fuel

ABSTRACT

A valve controlled supplemental air supply channel communicates with the air intake pipe in the fuel system of an internal combustion engine to deliver a supplemental supply of atmospheric air into said intake pipe at a location downstream of the throttle valve, the valve controlling the supplemental air supply being open to thus deliver the atmospheric air only when a vehicle powered by the said engine is coasting and the pressure in the intake passage is thereby reduced below the pressure which prevails in said intake passage during idling conditions of the engine.

United States Patent 1191 Pundt et al.

[ 1 MIXTURE CONTROL SYSTEM FOR AN INTERNAL COMBUSTION ENGINE WITH CONTROLLED INJECTION FUEL [75] Inventors: Dieter Pundt, Morse; Giinther Schmelzer, KleinSchoppenstedt, both of Germany [73] Assignee: Volkswagenwerk Aktiengesellschaft,

Wolfsburg, Germany [22] Filed: Apr. 8, 1971 [21] App1.No.: 132,300

[30] Foreign Application Priority Data Apr. 10, 1970 Germany 2017094 [52] U.S. Cl 123/97 B, 123/32 R, 123/32 EA, 123/139 AW, 123/119 D, 123/124 R [51] Int. Cl. F02d 33/02 58] Field 01 Search 123/97 B, 139 AW, 32 EA, 123/32 AE, 32 R, 119 D, 119 DB, 124 R,

1111 3,866,583 1451 Feb. 18, 1975 3,482,558 12/1969 Casey et al 123/139 AW 3,486,595 12/1969 Turner 123/97 B X 3,561,412 2/1971 Yagi 123/97 B 3,570,460 3/1971 Rabus 123/97 B 3,581,723 6/1971 Scholl 123/139 AW 3,613,650 10/1971 Stumpp 123/139 AW 3,661,131 5/1972 Croft 1.23/97 B 3,702,603 11/1972 Baxendale.... 1.23/97 B FOREIGN PATENTS OR APPLICATIONS 471,966 6/1969 Switzerland [23/97 B Primary ExaminerWendell E. Burns Attorney, Agent, or Firm-Watson, Cole, Grindle & Watson [5 7] ABSTRACT A valve controlled supplemental air supply channel communicates with the air intake pipe in the fuel system of an internal combustion engine to deliver a supplemental supply of atmospheric air into said intake pipe at a location downstream of the throttle valve, the valve controlling the supplemental air supply being open to thus deliver the atmospheric air only when a vehicle powered by the said engine is coasting and the pressure in the intake passage is thereby reduced below the pressure which prevails in said intake passage during idling conditions of the engine.

9 Claims, 4 Drawing Figures PATENTEDFEB18I9Y5 3, 866,583

SHEU 2 BF 2 v Fig.3

Fig. 4

IN VEN TOR a 7 M By/ Z Z MIXTURE CONTROL SYSTEM FOR AN INTERNAL QOMBUSTION ENGINE WITH CONTROLLED TNJECTION FUEL The invention relates to a mixture control system for an internal combustion engine with controlled fuel injection, whereby this control is to take place especially in accordance with variations in pressure of the intake pipe or the performance graph of the engine (effective performance graph control). By the term performance graph" of the engine is meant the load performance graph, therefore ultimately the connection between the torque and the r.p.m. of the engine, such as can be determined by means of a cam.

As is well known, the requirement exists to keep the harmful components of the exhaust gas at a minimum during the operation of an engine, for example of a motor vehicle. An operational state which in this respect is particularly important is the coasting operation. For instance, it has been sought to control the fuel injection through the proper designing of an electronic injection system in such a way that, in the case of coasting, the injection is switched off. However, this has the disadvantage that, after switching off, a resumption of the combustion must take place and these transitions can lead to jerky operation of the vehicle and noisy exhuast. Also, the cooling of the engine, which occurs as a result of the switching off of the vehicle injection, is undesirable in the case of extended downhill travel.

The mixture control system according to the invention, eliminates the need for switching off the engine during coasting for the purpose of improving the emission of exhaust gas and is characterized by the fact that an air supply channel is controlled by a valve operated in dependence on variations in operating values of the engine, such that the air supply channel is blocked during idling operation but is opened in the case of coast- Tn accordance with the invention, the fuel injection takes place in dependence on the intake pipe pressure or the performance graph of the engine. Thus, it is possible to improve the emission of exhaust gas to the desired extent in the coasting operation through an additional supply of air and through control of a supplemental air supply channel by means of a valve operated in the manner of a switch. The means required for this purpose are considerably less expensive than the apparatus required for a switch off of fuel injection during coasting.

Basically, there are two operational values of the engine which assume characteristic values during coasting and which are utilized accordingly for controlling the supply of additional air according to the invention in the case of the coasting operation. These on the one hand are the intake pipe pressure and on the other hand the r.p.m. of the engine.

If variations in the intake pipe pressure are relied upon for the supply of additional air during the coasting operation, then according to the invention the valve will be operated in dependence of variations in the intake pipe pressureand will be designed in such a way that the air supply channel will be opened only in the event the intake pipe pressure drops below the pressure within the intake pipe which occurs during idling.

One embodiment of the invention is distinguished by the fact that the air supply channel will be the intake pipe containing a throttle valve and the valve will be a spring loaded choke poppet valve supported by the throttle valve to control an air passage or opening through the throttle valve. The spring load of this choke poppet valve therefore has been adjusted in such a way that, in the case of the occurrence of a low pressure in the intake pipe such as occurs during the coasting operation, the valve is opened against the force of the spring. The poppet valve may be constructed very simply to comprise merely a disc which normally covers up one or more openings in the throttle valve, and which has a valve stem guided for operative movement through the throttle valve, and normally closed or seated by a compression spring.

Other embodiments of the invention, instead of employing the intake pipe as an air supply channel during coasting, provide an additional or supplemental air supply channel which delivers air from the atmosphere into the intake pipe at a location downstream of the throttle valve so as to by-pass the latter.

As is clear even from this first description of embodiments of this invention, given by way of example, this invention contains additional measures so that arrangements provided perhaps for the control of the other operational methods of the invention, for example for the idling operation, will not be influenced.

The valve may be arranged in the supplemental or by-pass channel in various ways; for instance in one embodiment it is a spring loaded ball valve, which the strength of the spring has been selected to permit opening of the valve at a predetermined pressure with a view to opening the supplemental air supply channel.

However, the valve may also be a diaphragm valve preferably one which is capable of automatically compensating for changes in atmospheric pressure. Such arrangements per se have been known; they permit an automatic adaptation, in an advantageous manner, of the regulating or control process to the outside atmospheric pressure. A corresponding valve will be developed in such a way that the diaphragm of the valve constitutes a movable wall of a first chamber which communicates with the atmosphere and of a second chamber which communicates with the: intake pipe by means of another valve independence on the difference between the intake pipe pressure and the atmospheric pressure.

The second principle of construction for the development of the invention is distinguished by the fact that the valve is operated in dependence on the r.p.m. of the engine and has been designed in such a way that the air supply channel will be opened only in the case of r.p.m. values lying above the idling r.p.m. and above a predetermined minimal r.p.m. value. This embodiment of the invention should be selected in the first place if an electronic control of the fuel injection also dependent on the r.p.m. is available, since in this case, one and the same tachometer can be used for the control of the injection in dependence on the method of operation of the engine and for the supply of the additional air in the case of coasting.

Basically, it also is possible in the case of this constructional principle to provide the throttle valve with an additional valve, for example a solenoid valve, which is operated by way of electric signals. However, an embodiment of the invention, in the case of which the air supply channel joins as a. by-pass in the intake pipe in the direction of the suction behind the throttle valve, will result in a less expensive construction as already described within the framework of the first construction principle. The valve can be a solenoid valve to which a tachometer supplying electric signals has been assigned. If in the case of the present engine we are dealing with an engine which is equipped with an automatic gear mechanism, which on its part contains a transformer, then one can again use a solenoid valve to advantage, the operating circuit of which upon switching the transformer on contains contacts operated in such a manner that then the air supply channel is opened. In this case the supply of the additional air is accomplished not only during coasting but also during the load operation of the engine. One can take this circumstance likewise into consideration in the case of designing (dimensioning) the throttle valve. Since the valve is opened even during standstill of the vehicle with a set transformer, the undesirable lowering of the idling r.p.m. will be avoided.

In the following paragraphs, the invention will be explained on the basis of an embodiment shown in the drawings by way of example.

In the drawings:

FIG. 1 is a diagrammatic sectional view through a portion of an internal combustion engine incorporating a preferred embodiment of the invention.

FIG. 2 is a view similar to FIG. 1, but showing a second embodiment.

FIG. 3 is a view similar to FIG. 1, showing a third embodiment of the invention.

FIG. 4 is a diagrammatic view through a portion of a conventional internal combustion engine of the fuel injection type to which the present invention is applied.

Referring now in detail to the accompanying drawings, and first considering the conventional engine structure shown in FIG. 4, it will be seen that the air supply channel or an extension thereof 1, communicates with and delivers the supply of air directly to the intake port 25 of an engine cylinder 26. Both the inlet port 25 and also the exhaust port 27 of the cylinder 26 are controlled by conventional tappet valves 28 and 29 as shown. The fuel injection valve 30 has its discharge end located closely adjacent the intake port 28 and directed toward such port so that fuel delivered under pressure to the injection valve 30 through a fuel line 31 is injected through the port and into the cylinder in timed relation to the opening of the intake valve 25, under the control of electrical impulses supplied through the electrical circuit 32. Obviously, the arrangement of the injection valve 30 with respect to the intake port 28 is such that the formation of a combustible mixture of fuel and air is accomplished only upon intermingling of the spray or jet of fuel with the air within the engine cylinder 26. Where the air and the fuel are thus separately delivered to the cylinder the quantity of fuel to be supplied on each injection is capable of adjustment independently of the air supply, and likewise the volume of air supplied and the air pressure are capable of adjustment independently of the fuel, so that it is possible to regulate the relative proportions of air and fuel in the resulting mixture within the cylinder accordingly.

In the embodiment according to FIG. 1, the throttle valve 2 is mounted for pivotal movement around axis 3 in the customary manner in the intake pipe 1. There is provided a supplemental air channel by-passing the throttle valve 2 and formed by the channel portions 4 and 5, which air channel delivers air into the intake pipe when the throttle valve is closed during idling. The numeral 6 designates an adjusting screw which permits the adjustment of the effecive cross section of the channel 4, 5.

The channel portion 4 extends via an annular channel portion around and past the adjusting screw 6 to the valve disc 7, which is a component of a normally closed main valve, the operating mechanism of which is shown in the right-hand part of FIG. 1, and which is opened to establish communiction between channel portions 4 and 8 only when the engine is in coasting operation. The valve disc 7 is carried by a stem 10 for movement into and from closed or sealing relation in the valve seat 11 of channel portion 8. As is also true in the other illustrated embodiments, the construction of the valve in FIG. 1 is such that its operation is in response to variations in the pressure in the intake pipe 1. For this purpose, the valve 7 is carried via its stem 10 by a diaphgram 9. Diaphragm 9 constitutes a movable partition between the two pressure chambers 12 and 13, of which chamber 12 communicates through channel 14 with the outside atmosphere and chamber 13 communicates with the atmosphere via constricted passage 15. As can be seen, chamber 17 of the additional valve 16 is connected with the intake pipe 1 via channel 18.

The method of operation of this valve arrangement is as follows:

In the case of all operational conditions of the engine except in coasting, the main valve 7 is closed by the action of spring 19, since the pressure on opposite sides of its diaphragm 9 are substantially equal. Also, the valve body or control valve 20 is in its closed position as shown, since the strength of compression spring 21 is such that it is able at all times, except during coasting of the vehicle to overcome valve unseating forces aris' ing from differential pressures on opposite sides of the diaphragm 22 in chambers 17 and 23. The diaphragm 22 of the additional valve 16, furthermore, is under action of the barometric altimeter 24, so that the measurement of the variance between the pressure in the intake pipe 1 on the one hand and in the atmosphere on the other hand, which is decisive for the release of channel 4, 8, is corrected automatically according to the pertinent altitude.

As soon as the pressure in intake pipe 1 drops below a determined value, which occurs as the vehicle begins to coast, said pressure is transferred via channel 18 into chamber 17 so that the pressure of spring 21 will be overcome and valve body 20 will be opened or unseated. As a result, chamber 13 of the main valve will be placed in communication through chamber 17 and passage 18 with intake pipe 1, so as to be subjected to the relatively low sub-atmospheric pressure of pipe 1, and correspondingly, the valve disc 7 is lifted from valve seat 11. As a result, the portions 4 and 8 of the supplemental air channel are connected with one another and now form a continuous air supply channel which by-passes the throttle valve 2.

As soon as coasting has been concluded, the additional valve 16 closes again and atmospheric air is bled into the chamber 13 through the constricted passage 15 so that the diaphragm 9 is acted upon to close or seat the main valve 7.

In FIG. 2 the elements already shown in FIG. I have been provided with the same reference numerals. While a diaphragm valve was used in the embodiment of FIG. 1, the embodiment according to FIG. 2 is equipped with a spring loaded ball valve 30, whereby the barometric correction for altitude has been omitted. The ball valve consists essentially of ball 30 which is forced by the spiral spring 31 against seat 32 in the housing. As a result, the two portions 4 and 32 of the supplemental air channel are sealed from one another in all operational states of the engine except in coasting, through incoming air may flow into the intake pipe 1 through interconnected channel portions 4 and 5 during idling. Spring 31 has been dimensioned in such a way that ball 30 is lifted off seat 32 as soon as the pressure in intake pipe 1 drops below a value characterizing the coasting operation. The air supply channel for coasting operation provided according to the invention is then formed by parts 4, 32 and 5 of the channel connected with one another.

In the embodiment according to FIG. 3 given by way of example, the intake pipe itself is utilized as an air supply channel. For this purpose the choke poppet valve designated generally as 40 is mounted on the throttle valve 2. The choke poppet valve consists essentially of the valve disc 41 with the valve stem 42 and the compression spring 43. In the area of valve disc 41, openings 44 in a suitable number have been provided in throttle valve 2, which are covered by valve disc 41 during all operational states of the engine except during coasting by means of valve disc 41 under the resilient action of spring 43. However, as soon as the pressure in the area of intake pipe 1 on the downstream side of throttle valve 2 drops below a predetermined pressure value in consequence of the beginning of coasting, valve disc 41 can be unseated from the surface of throttle valve 2, counter to the action of spring 43, to un' cover the openings 44 so that additional air can find its way through these openings.

Having thus described my invention, I claim:

1. A mixture control system for an internal combustion engine of the fuel injection type for supplying both fuel and air during a coasting operation wherein air and fuel are delivered separately to the intake part of each engine cylinder and wherein the fuel injection is regulated in dependence on the air intake pipe pressure, characterized in the provision of an air supply channel,

, a valve controlling the flow of air through said channel and operated in dependence on operational values of the engine, which values in the coasting operation assume characteristic values, said valve closing the air supply channel during idling but opening it during coasting so as to enable additional air to be supplied.

2. A mixture control system according to claim 1 characterized in that the valve is operated in dependence on the intake pipe pressure and has been designed in such a way that the air supply channel is opened only when the intake pipe pressure drops below the pressure which prevails in the intake pipe during idling.

3. A mixture control system according to claim 2, characterized in that a throttle valve is operatively disposed in said intake pipe and the air supply channel acts as a by-pass and communicates with the intake pipe at a location downstream of the throttle valve.

4. A mixture control system according to clalim 2, characterized in that the valve is a diaphragm valve.

5. A mixture control system according to claim 4, characterized in that the diaphragm valve contains an arrangement for taking the atmosphereic pressure into consideration.

6. A mixture control system according to claim 1 wherein said valve is a spring loaded ball valve.

7. A mixture control system according to claim 1 wherein the air supply channel is an intake pipe, said valve is a throttle val-ve disposed in controlling the flow of air through said pipe, said valve being a spring loaded choke poppet valve mounted on and controlling an opening through said valve.

8. A mixture control system for an internal combustion engine wherein the fuel injection is regulated in dependence on its intake pipe pressure (or its performance graph), characterized in the provision of an air supply channel, a valve controlling the flow of air through said channel and operated in dependence on operational values of the engine, which values in coasting operation assume characteristic values, said valve closing the air supply channel during idling but opening during coasting, said valve being; a diagphragm valve which is operated in dependence on the intake pipe pressure and has been designed in such a way that the air supply channel is opened only when the intake pipe pressure drops below the pressure which prevails in the intake pipe during idling, said diaphragm valve containing an arrangement for taking the atmospheric pressure into consideration, and being characterized by the fact that the diaphragm of the valve consistutes a yieldable partition between a first chamber containing air under atmospheric pressure and a second chamber communicating with the intake pipe, there being an additional valve controlling communication between said second chamber and the intake pipe in dependence on the difference between the intake pipe pressure and the atmospheric pressure.

9. A mixture control system for a fuel injection type internal combustion engine to which during a coasting operation, while maintaining a supply of fuel, atmospheric air is admitted through an intake pipe under the control of a throttle valve interposed in said intake pipe, wherein the improvement comprises: means defining a supplemental air channel by-passing said throttle valve for delivering atmospheric air into said intake pipe at a location downstream of said throttle valve; a second valve controlling the flow of air through said channel; means resiliently urging said second valve to a closed position; and means responsive to pressure in said intake pipe at a location downstream of said throttle valve for opening said second valve only when the pressure at said location drops below the pressure which prevails at said location during idling of the engine so as to enable additional air to be supplied during such coasting operation. 

1. A mixture control system for an internal combustion engine of the fuel injection type for supplying both fuel and air during a coasting operation wherein air and fuel are delivered separately to the intake part of each engine cylinder and wherein the fuel injection is regulated in dependence on the air intake pipe pressure, characterized in the provision of an air supply channel, a valve controlling the flow of air through said channel and operated in dependence on operational values of the engine, which values in the coasting operation assume characteristic values, said valve closing the air supply channel during idling but opening it during coasting so as to enable additional air to be supplied.
 2. A mixture control system according to claim 1 characterized in that the valve is operated in dependence on the intake pipe pressure and has been designed in such a way that the air supply channel is opened only when the intake pipe pressure drops below the pressure which prevails in the intake pipe during idling.
 3. A mixture control system according to claim 2, characterized in that a throttle valve is operatively disposed in said intake pipe and the air supply channel acts as a by-pass and communicates with the intake pipe at a location downstream of the throttle valve.
 4. A mixture control system according to clalim 2, characterized in that the valve is a diaphragm valve.
 5. A mixture control system according to claim 4, characterized in that the diaphragm valve contains an arrangement for taking the atmosphereic pressure into consideration.
 6. A mixture control system according to claim 1 wherein said valve is a spring loaded ball valve.
 7. A mixture control system according to claim 1 wherein the air supply channel is an intake pipe, said valve is a throttle valve disposed in controlling the flow of air through said pipe, said valve being a spring loaded choke poppet valve mounted on and controlling an opening through said valve.
 8. A mixture control system for an internal combustion engine wherein the fuel injection is regulated in dependence on its intake pipe pressure (or its performance graph), characterized in the provision of an air supply channel, a valve controlling the flow of air through said channel and operated in dependence on operational values of the engine, which values in coasting operation assume characteristic values, said valve closing the air supply channel during idling but opening during coasting, said valve being a diagphragm valve which is operated in dependence on the intake pipe pressure and has been designed in such a way that the air supply channel is opened only when the intake pipe pressure drops below the pressure which prevails in the intake pipe during idling, said diaphragm valve contaiNing an arrangement for taking the atmospheric pressure into consideration, and being characterized by the fact that the diaphragm of the valve consistutes a yieldable partition between a first chamber containing air under atmospheric pressure and a second chamber communicating with the intake pipe, there being an additional valve controlling communication between said second chamber and the intake pipe in dependence on the difference between the intake pipe pressure and the atmospheric pressure.
 9. A mixture control system for a fuel injection type internal combustion engine to which during a coasting operation, while maintaining a supply of fuel, atmospheric air is admitted through an intake pipe under the control of a throttle valve interposed in said intake pipe, wherein the improvement comprises: means defining a supplemental air channel by-passing said throttle valve for delivering atmospheric air into said intake pipe at a location downstream of said throttle valve; a second valve controlling the flow of air through said channel; means resiliently urging said second valve to a closed position; and means responsive to pressure in said intake pipe at a location downstream of said throttle valve for opening said second valve only when the pressure at said location drops below the pressure which prevails at said location during idling of the engine so as to enable additional air to be supplied during such coasting operation. 